Early vehicles were relatively simple in construction and were relatively easy to diagnose and repair. However, it was sometimes necessary to road test the vehicle in order to diagnose certain problems. As motor vehicles became more sophisticated in construction, diagnosis and repair became more difficult. In order to simplify the testing procedure and to enable the mechanic to obtain more consistent test conditions, chassis dynamometers were developed to enable a vehicle to be "road tested" while remaining stationary in a repair or test facility.
Because chassis dynamometers drive or are driven by the tires of the vehicle being tested, they are able to detect not only the power output of the engine, but are also able to detect the parasitic horsepower, or friction losses caused by the drive train and other components. Motors, retarders, water brakes, flywheels and a variety of braking devices are used to either power the rolls or to provide resistance, thereby enabling power and/or braking performance to be checked under simulated road conditions. Conventional chassis dynamometers, however, are able to perform only a limited number of tests, generally confined to measuring the horsepower or braking effectiveness of the vehicle being tested.
Fleet operators, repair garages and testing laboratories sometimes utilize a chassis dynamometer for diagnostic purposes. However, because of the relatively narrow range of tests capable of being performed with conventional chassis dynamometers, and their relatively high cost, many fleet operators and repair garages do not have a chassis dynamometer. Equipment used by testing laboratories is capable of performing a wide range of diagnostic tests, but is much too complex and expensive to be purchased and operated by most facilities. Consequently, the use of a chassis dynamometer to diagnose the performance of a vehicle has generally been limited in the past to vehicle manufacturers, race car repair shops and more sophisticated repair facilities.
Current automotive technology has reached new levels of sophistication, relying on computers and complex engine, transmission and braking systems, and conventional chassis dynamometers have not kept pace. As a result, many tests that would be beneficial with new automotive technology cannot be satisfactorily performed in the field with conventional chassis dynamometers. Such capabilities generally exist only in the facilities of automotive manufacturers and testing laboratories.
Notwithstanding these shortcomings with conventional chassis dynamometers, there is increased need to be able to optimize the performance of motor vehicle systems. The number of vehicles on the road increases each year, with a concomitant increase in motor vehicle accidents, and greater levels of air pollution and other damage to the environment, Inadequate or improper performance of motor vehicles not only reduces safety and increases damage to the environment, but also increases fuel. In an effort to relieve these conditions, automotive inspections are required so that defective components or inadequate performance can be detected and corrected. However, these inspections are carried out with only the most rudimentary types of equipment, typically with the vehicle standing still and not under conditions simulating actual performance on the road.
Legislation has recently been enacted with the objective of improving air quality and safety. For instance, the Environmental Protection Agency has enacted regulations requiring enhanced inspection and maintenance programs for motor vehicles in order to monitor and enforce new standards for vehicle emissions as mandated in the Clean Air Act of 1990. While this is a commendable step in the right direction, typical motor vehicle inspection and repair stations do not have the facilities or equipment to test vehicles in a way that will simulate actual road conditions and thereby enable correction of defects that may only show up at certain speeds and under certain conditions, i.e., with the vehicle under load.
There is thus need for a simple and inexpensive testing apparatus that is easy to use, is capable of testing a variety of vehicle components, including engine performance, braking effectiveness and wheel alignment, and that may be installed by even small testing and repair facilities to thereby maximize the number of vehicles which may be tested under simulated road conditions.